I've just played L4D2 Survival for 2 maps, The Port of The Passing and The Generator of No Mercy. I got a gold medal and silver one. But when I check my L4D2 stats, it didn't show any new stats that I have played. My friends are the same as me.

Is this a problem? L4D2 Leaderboard also doesn't show any new Survival map, The Generator - No Mercy, for example.

Make sure you are connected to the steam servers before making anything that's stats wise, because if you're not it'll end up being not registered. From that i can tell while playing Dead Spce 2 with my PC specs, i cleared the game but i can't even connect to the chat and so on, leading me to be offline and not register hours i've been on it. You can try putting steam.exe in a higher priority, but this'll can maybe affect your game performance depending on what you're using, if you do have a nice setup, then i guess you were unlucky and not have been connected during that.

If you played on a modded server (such as noobtoob) then your time will show only on that server. The times don't show on official dedicated servers, or your stats.

EDIT: Misread your post. No mercy and the Port Sacrifice were never added to the leaderboards or survival stats page. If you mean port sacrifice, then that's why.

If it was port passing (assuming the server wasn't modded), then it must've been a bug that didn't register your time. I've only seen that happen to one other person though so I don't think it's a common thing at all. (look at the comment sec of the screenie):http://steamcommunity.com/sharedfiles/filedetails/?id=140996047

Well sometimes the server can be slightly modded, and it would still keep the time (I think) in some situations. Not completely sure about that for all modded servers, but yeah, best thing is to choose official dedicated if you want the time to save xD